P25BF code meaning
Alternative Fuel Disable Control Circuit High
Powertrain system Generic code P25xx codes Check engine light
What P25BF means
P25BF flags a voltage on the alternative fuel disable output that is too high for the state the engine controller is commanding. On a low-side driver this usually means a short to battery or ignition voltage, for instance where a gas kit harness has been routed along a hot feed or tapped into the wrong wire. Depending on design, a constantly high line may be read by the gas system as a permanent block, or the controller may switch the driver off to protect itself; either way the command it sends is no longer trustworthy. GM's 2016 Silverado and Sierra bi-fuel trucks show what the driver sees when gas operation is refused: the fuel indicator flashes and the truck stays on gasoline. No manufacturer documents P25BF publicly. Note that SAE lists High before Low in this group.
P25BF at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P25BF
- Gas operation blocked, vehicle runs on gasoline only
- Fuel mode indicator flashes
- Check engine lamp
Common causes of P25BF
- Most likelyControl wire shorted to battery or ignition voltage
- PossibleRetrofit gas kit tapped into the wrong circuit
- Less likelyFaulty input stage in the gas controller backfeeding voltage
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Alt fuel control moduleWiring harness
What each part of P25BF means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| BF | The exact fault in that area. |
What to do next
- Note P25BF and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P25BF
What does P25BF mean?
P25BF means "Alternative Fuel Disable Control Circuit High". P25BF flags a voltage on the alternative fuel disable output that is too high for the state the engine controller is commanding. It is a generic code, so it means the same on every make.
Is it safe to drive with P25BF?
Drive gently and only to a workshop. With P25BF the car can go into limp mode (reduced power) to protect itself.
Will P25BF fail an emissions test?
Yes, it can. P25BF is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P25BF to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P25BF clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.